Accuracy of Bispectral IndexTM monitoring in an alternative nasal position in pediatric patients under general anesthesia: a prospective observational study

Purpose: The standard frontal Bispectral Index™ (BIS™) monitoring during anesthesia is clinically validated; nevertheless, alternative sensor positions may be necessary when the forehead is inaccessible. We aimed to evaluate the accuracy of BIS monitoring obtained from the nasal region compared with conventional frontal placement in pediatric patients under general anesthesia. Methods: We included 40 children (aged 4–12 yr) undergoing general anesthesia with sevoflurane in a prospective observational study. We placed pediatric BIS sensors on the forehead and over the nasal bridge and the ipsilateral temporal region. We assessed the agreement between nasal and frontal BIS values. We performed subgroup analyses during different anesthetic phases, electromyography (EMG) activity, and age group. We then compared the power spectral density between nasal and frontal placements. Results: We analyzed 5,049 artifact-free paired BIS measurements. The mean (standard deviation) difference between nasal and frontal BIS values was 1.0 (4.5) (95% limits of agreement, −8 to 10), with a good correlation (concordance correlation coefficient, 0.88). The marginal incidence of BIS values exceeding the ±10-unit acceptable threshold was 3.9% (95% confidence interval [CI], 2.1% to 5.8%), with a higher marginal incidence exceeding acceptable limits during emergence (6.6%; 95% CI, 1.3% to 11.8%) and in the high-EMG group (8%; 95% CI, 1% to 15%), and was similar across age groups. Spectral characteristics were comparable, with lower total power at the nasal position. Conclusions: Bispectral Index values obtained from the nasal region in pediatric patients agreed within ±10 units of the values from conventional frontal placement. Scalp flap dissection or contamination may alter impedance; thus, BIS should be interpreted cautiously with the density spectral array, ensuring stable impedance for reliable signals.